1. Field of the Invention
This invention is in the field of multiple-roller conveyors providing support for objects between adjacent shafts.
2. Description of the Prior Art
Conveyors are employed in various fields to transport objects along a pathway or over a distance. These conveyors typically comprise one of two types, the belt conveyor and the roller conveyor. In the first type, the conveyor includes a continuous belt which extends over rotatable rollers. The rollers are driven by a motor to move the belt and to transport the objects which are supported thereon. The second type of conveyor incorporates rollers which are rotatably mounted on a shaft, the transported objects resting directly upon the rollers. The rollers either depend upon the force of gravity acting on the objects to move the objects down the conveyor line, or the rollers are positively driven by a motor.
For roller conveyors, the transported objects are supported on a discontinuous surface area defined by the tops of the rotatable rollers. The rollers therefore must carry the weight of the objects and must keep the objects balanced and upright. The base of each object should rest on a plurality of rollers on a shaft and on rollers on a plurality of adjacent shafts to be sufficiently supported to remain upright. The spacing between the shafts therefore is critical with respect to the size of the transported objects.
The spacing between shafts having large rollers is necessarily greater than for shafts having small rollers. As a result, there is generally a limitation on the maximum size of rollers which may be utilized for transporting a given object. If the rollers are too large, the distance between the tops of the rollers on adjacent shafts may be so great as to result in the objects falling over from lack of balanced support. As a general rule, the shortest lateral dimension of the base of the transported object should not be less than twice the distance between the tops of rollers on adjacent shafts. This would provide for the transported objects being supported by rollers on at least two adjacent shafts at any given time along the conveyor. It is preferable, however, that the shortest dimension of the base of the object be not less than three times the distance between the tops of rollers on adjacent shafts, in order to ensure the smooth, continuous flow of the objects along the conveyor.
As a result of the above-described limitations, the multiple-roller conveyors having large rollers have not previously been adaptable to transportation of small objects. An operation which utilizes a conveyor having large rollers may be temporarily or permanently abandoned. It may then be desirous to use that conveyor, in order to conserve money, in a new or different operation. In light of the size restrictions noted above, the large roller conveyor could not previously be used to transport items which were too small in relation to the size of the rollers.
A need has therefore arisen for an improved multiple- roller conveyor which would support and balance objects of a size smaller than would otherwise be possible based strictly on the size of the rollers. Such a conveyor has not been developed in the relevant prior art. In U.S. Pat. No. 2,897,953, issued to Namenyi-Katz on Aug. 4, 1959, there is disclosed a conveyor system which utilizes several parallel, co-planar shafts, each shaft having a plurality of cylindrical rollers mounted thereon. The cylindrical rollers are mounted in side-by-side relation and are mechanically driven by pressurized gas acting upon internal vanes of the rollers. U.S. Pat. No. 3,337,023, issued to Kohl et al. on Aug. 22, 1967 discloses a conveyor system which similarly has a plurality of rollers mounted upon each of several shafts. In neither of these patents, however, is there disclosed a means for supporting the transported objects other than by the tops of the rollers, and neither provides for adapting the conveyor to transport objects of a size smaller than would otherwise be possible.
In my U.S. patent application, Ser. No. 467,090, now issued as U.S. Pat. No. 3,951,255, there is also disclosed a conveyor having a plurality of rollers on each shaft. The present invention may be used with this and other multiple-roller conveyors to provide an improved conveyor which is capable of transporting objects of a size smaller than would normally be possible.